Semihard rubber composition and method of making same



Patented Apr. 22, 1952' SEMIHARD RUBBER COMPOSITION AND METHOD OF MAKING SAME John R. Helms, Akron, om Goodrich Company, Ne

ration of New York 0, assignor to The B. F.

w York, N. Y., a corpo- No Drawing. Application J une 9, 1949,

Serial No. 98,167

Claims. (01. 260--763) This invention relates to a semi-hard rubbery composition and pertains more particularly to a semi-hard rubbery tire and the method of making it.

It is an object of my invention to provide a semi-hard rubbery tire having improved blowout resistance.

It is also an object of my invention to provide a semi-hard rubbery composition having improved resistance to cutting and chipping.

Another object of my invention is to provide a semi-hard rubbery tire composition which has improved traction properties on smooth surfaces and which requires less power to overcome surface-tire friction when propelling machinery using tires made of such composition.

A further object of my invention is to provide a semi-hard rubbery composition possessing low hysteresis properties.

Other objects of my invention will be apparent from the description which follows.-

My invention is particularly adapted for use in industrial tires as used for example on material-handling fork pallet type trucks or similar equipment where a small diameter wheel is subjected to heavy loads; such tires are of the nonpneumatic type.

Heretofore, tires used on this type of equipment have been susceptible to cutting and chipping and heat build-up causing blow-outs. 'F'urthermore. conventional industrial tires have unsatisfactory traction properties on smooth surfaces, and consume an undesirable quantity of power in motivating industrial vehicles on such surfaces.

I have discovered an improved semi-hard rubbery composition particularly adapted for use in industrial tires having improved traction. on smooth surfaces, thereby permitting industrial equipment to be motivated with relatively little power consumed. Furthermore, my invention provides a, material which exhibits increased blow-cut resistance, improved cuttingand chipping resistance, and lower hysteresis properties as compared to known materials used for tires on such equipment.

easy processing channel black, dispersed homogeneously in specified proportions throughout the elastomeric material.

Throughout the rubber industry carbon blacks have been the primary reinforcin materials in oorporated in rubber or rubbery materials. The method of manufacturing carbon blacks in general involves the incomplete combustion of net 1 Percent volatile mini} .ural gas or oil and recovery of the particles of carbon from the gases of combustion. The carto chemical reaction and/or a physical phenomenon.

Semi-reinforcing furnace black is manufactured by the incomplete combustion of natural gas or oil in a heated furnace.

Property y Oil absorption factor Percent DIG adsoryitiom.

Easy processing channel black is generally produced .by the incomplete combustion of natural gas which is ignited at the tips or small burners, and the gas stream containing the particles of carbon is directed against a channel or'metal plate onto which the carbon particles Scrapers dislodge the carbon particles from" the channel and the carbon black falls into hoppers and is collected. Carbon black of this type is easy processing, highly reinforcing, possesses relatively cool mixing characteristics, im-

parts fast curing? properties to rubbery composicapto thiazyl and 15% properties 2 1 Range Property tv Min. Max. My; Surface area (sq. rnJgni.) 105.0 1 135.0 Calculated average part1 e diameter (m I 20.0 35.0 pH 3.5 5. 5 Percent volatile matter" I 4. 6. Oil absorption factor. 105. 0 125. 0 7. 5 l4. 5

Percent DPG adsorptioi n In the composition of this invention the desired properties may be obtained by dispersing into 100 parts by weight of natural rubber, such ascaoutchouc and the like, to 60 parts by weight of easy processing channel black, to 100 parts by weight of semi reinforcing fur.- naceblack, and 3 to 7 parts by w'eightof sulfur. :Any of, the usual fillers, softeners, accelerators, age resistors, etc'., which are commonly-used in the rubber industry may be employed in my composition, if desired. The rriost satisfactory results are obtained by dispersing into. 1'0( parts by weight of natural rubber 2:0 to parts by weight of easy processing .channel blaclg to 80 parts by weight of semi-reinforcing furnace black, and 3 to 7' parts by weight of Slll'flll'..

Any accelerator generlly added to! rubbery compositions may improvements in cutting and chipping, etc. being obtained. It is preferable, however, to use from 1.0 to 1.5 parts by weight of an alkyl mercapto thiazole type accelerator, such as mixeddialk'yl mercapto thiazoles, disulfide of mixed dialkyl mercapto thiazole, etc.,.to" acquire the optimum results. A mixture of 85% by weight of 4,5-dimethyl merby weight of l-ethyl mercapto thiazyl and a mixture of 85% by weight at least an equal amount by weight of natural rubber since natural rubber imparts the most favorable hysteresis properties to the compo. sition.

It is not understood why a mixture of semi-reinforcing furnace black and easy processing "channel black, when dispersed in specific proportions into a rubbery composition, imparts to the vulcanized composition the properties desired, such as improved blow-out resistance, improvedresistance to cutting and chipping, im

' proved traction, etc. However, I must conclude interaction of the forcing furnace black or be used in my invention with 4 traction, blow-out resistance,

of his (4,5-dimethyl thiazole) disulfi-de and 1 5% bis (e-ethyl thiazole) disulfide are particularly satisfactory accelerators, in that they impart to vulcanized rubbery compositions excellent hysteresis properties. Any'alkyl mercapto thiazole or alkyl thiazyl disulfide having .from 1 to 5 vcarbon'aton'is in each alkyl group will likewisegive excellent results. v i d I An industrial rubbery tireltnat issubiected in use to heavy loads must be sufiiciently rigid, so that it will not contour, but must not be so rigid that it is brittle and----splits under the stresses normally exerted uponit. To meet this requirement at rubbery composition having a-minimum durometer A flow and deform from its general hardness of 80 points and a maximum'durometer A hardness of 90 points is preferably used.

Although it is preferable to use natural rubber which is essentially a rubbery polymer of isoprene as the sulfur-vulcanizable elastomeric material, synthetic rubber may also be used, such. as the rubbery polymers of..open-chained conjugated diol'efins having from 4 to 8 carbon atoms exemplified by butadiene-1,3;-2,3-dimethyl butadiene-1,3;' .1-,4-dimethyl butadiene-L3; and the like, or the copolymers of these and similar materials with each other or with such copolymerizable monomeric ethylenic materials .as styrene, acrylonitrile methyl acrylate, methyl methacrylate, ethyl acrylaterethyl methacrylate; isobutylene, and similar. materials; I

It is preferableyhoweven if syntheti'crubber is to be used to blendthe synthetic rubber with that these properties are obtained due to the two types of carbon blacks on the rubbery material, since, if either semi-reineasy processing channel blackis used alone, the desired properties are not obtained.

I Examples of compositions prepared in accordance with; my invention are illustrated by the following-recipes which are included merely for purposes of illustration, and are not intended to limit the scope of this invention.

Example I A composition having the following recipe was prepared by mixing the ingredients in the usual manner on a roll mill:

Material by Natural rubber Easy processing channel black Semi-reinforcing furnace black Zinc oxide Sulfur.

Antioxidant Disulflde 0i amixed dialkyl mercapto thiazole Total proved traction characteristics on smooth surfaces,; improved resistance to cutting and chipping, and-lower hysteresis properties as compared to known industrial tire compositions.

Example II A typical example of a composition embodying my invention using a blend of natural rubber and synthetic rubber is as follows:

Material Natural rubber Rubbery butadiene-styrene copolyiner (GR-S) (72% eon- Easy processing channel black u Semi-reinforcing furnace black Zinc-oxide Antioxidant r Disulfide of a mixed dialkyl mercapto thiazo1e.

in a mold at The composition may be mixed and vulcanized as in Example I wit physical characteristics and physical tests of the same magnitude being obtained.

Example III A typical example of a composition embodying my invention using {synthetic rubber as the sulfur-vulcanizable elastomeric material is as follows: j

I Parts Almeria] 1 y I weight Rubbery)butadiene-sryrene copolyzner (GR-S) (72% conversion 100. Easy processing channel bla 1'40. 0 Semi-reinforcing furnace black. 55. U Suliur 4. 0 Softener..- 2. Antioxiden 1. 4 Disulfide of a mixe i. l Zinc oxide 8. 5

The composition may be mixed and vulcanized as in Example IIwith physical characteristics and physical testsof the same magnitude being obtained.

The compositions cited in the examples above which embody my invention provide the improvements desired, such as low hysteresis properties, greater blow-out resistance, greater adhesion to smooth surfaces with lower power consumption, etc., asjset out above.

It is obvious that my invention is susceptible canized in the presence of from 3 to 7 parts by weight of sulfur.

2. A vulcanized tire comprising 100 parts by weight of a vulcanized crude rubber, to 40 parts by weight of easy processing channel black, 50 to 80 parts by weight of semi-reinforcing furnace black, and 1.0 to 1.5 parts by weight of an alkyl mercapto thiazole type accelerator, vulcanized in the presence of from 3 to 7 parts by weight of sulfur.

3. A vulcanized composition comprising 100 parts by weight of crude rubber, 20 to 40 parts by weight of easy processing channel black, and 50 to 80 parts by weight of semi-reinforcing furnace black. vulcanized in the presence of from 3 to 7 parts by weight of sulfur.

to numerous substitutions of equivalent materials or variations in quantity of materials used without departing from the spirit and scope of my invention as defined in the appended claims.

I claim:

1. A vulcanized composition comprising 100 parts by weight of crude rubber, 20 to parts by weight of easy processing channel black, to parts by weight of semi-reinforcing furnace black, and 1.0 to 1.5 parts by weight of an alkyl mercapto thiazole type accelerator, vul- 4. A vulcanized tire comprising parts by weight of a vulcanized crude rubber, 20 to 40 parts by Weight of easy processing channel black. and 50 to 80 parts by weight of semi-reinforcing furnace black, vulcanized in the presence of from 3 to 7 parts by weight of sulfur.

5. The method of making a rubbery composition comprising dispersing 20 to 40 parts by weight of easy processing channel black, 50 to 80 parts by weight of semi-reinforcing furnace black and 3 to 7 parts by weight of sulfur into 100 parts by weight of crude rubber and vulcanizing the composition to a semi-hard elastomeric material.

JOHN R. HELMS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name I Date 1,930,437 Beaver Oct. 10, 1933 2,449,461 Elliott et al Sept. 14, 1948 OTHER REFERENCES India Rubber World, vol. 107 of January 1943, pages 365-368. 

1. A VULCANIZED COMPOSITION COMPRISING 100 PARTS BY WEIGHT OF CRUDE RUBBER, 20 TO 40 PARTS BY WEIGHT OF EASY PROCESSING CHANNEL BLACK, 50 TO 80 PARTS BY WEIGHT OF SEMI-REINFORCING FURNACE BLACK, AND 1.0 TO 1.5 PARTS BY WEIGHT OF AN ALKYL MERCAPTO THIAZOLE TYPE ACCELERATOR, VULCANIZED IN THE PRESENCE OF FROM 3 TO 7 PARTS BY WEIGHT OF SULFUR. 